Mounting a sign plate generally radially to a post creates problems different from those where the post is secured to the rear of the sign. In the latter case, the post can be mounted in the middle of the sign, or two or more posts can be used if necessary, and channel or other reinforcing members can be secured to the rear of the sign plate. With offset signs, however, the post has to be secured to one side edge of the sign, thereby requiring a special type of mounting device. Usually only one post can be used, so that the mounting has to support the full cantilever weight of the sign. Also the sign usually has indicia on both surfaces so that any reinforcing members have to be restricted to the top and bottom edges without obscuring the sign surface. Finally, the whole arrangement should be as neat as possible so as to be visually acceptable, while keeping the cost of the sign within acceptable limits. Associated with this is the desirability of having a mounting device which can be used with a variety of different size signs and posts.